Several recent hypotheses suggest that cell recognition and growth are regulated in large part by epigenetic alterations in the structure of cell surface receptors as well as by changes in the receptor mobility and distribution. Bone marrow derived lymphocytes (B cells) provide a unique model for studying the regulation of eukaryotic cells since B cells possess membrane associated antigen-binding receptors. Ligands binding to the receptors may initiate either specific activation or specific suppression of cellular proliferation and differentiation. Receptors are present on precursors of antibody-forming cells as well as on immature antibody-forming cells. The receptors appear to be lost through differentiation since they are not detectable on mature antibody-forming cells. I propose to study and compare the dynamics of receptors on a normal and a neoplastic antibody-forming cell pair following the interaction of the receptors with either a stimulator ligand or a suppressor ligand. The cells of the normal and neoplastic cell pair that I will use are identical in at least two respects, i.e., they each synthesize and secrete a structurally identical anti-dextran antibody, and each cell possesses receptors which bind dextran. Dextran B1355 stimulates the proliferation of normal anti-dextran antibody-forming cells while the same dextran, when oxidized, specifically suppresses the normal proliferative response. The oxidized dextran also specifically suppresses the in vivo proliferation of the neoplastic anti-dextran antibody-forming cell. In the present study, changes in the receptor (i.e., pattern of distribution and mobility, rate of shedding, and re-expression) following interaction with dextran or oxidized dextran will be monitered in the normal and neoplastic cell pair. An attempt will be made to integrate the receptor dynamics induced by dextran or oxidized dextran with alterations in cell function, i.e., protein synthesis and secretion, differentiation, DNA synthesis and mitosis. A causal relationship between the receptor dynamics and cell function will be tested by introducing dextran or oxidized dextran directly (without receptor perturbation) into the cell via a unilamellar lipid carrier vesicle.